Lower-leg exoskeleton system and method

ABSTRACT

A lower-leg exoskeleton that includes an actuator configured to be worn about a portion a leg of a user that is below the knee of the user; and a foot structure coupled to a first actuator end of the actuator, the foot structure configured to surround a portion of the foot of the user. The foot structure includes one or more sidewalls configured to extend around the foot of the user and including one or more sidewall attachment points for connecting to a base portion, and a base portion configured to reside at a base of the foot of the user and including one or more base attachment points coupling with the one or more sidewall attachment points.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/708,122, filed Dec. 9, 2019, which is a continuation of U.S.application Ser. No. 15/082,824, filed Mar. 28, 2016, now U.S. Pat. No.10,543,110, which is a non-provisional of and claims the benefit of U.S.Provisional Application No. 62/139,184 filed Mar. 27, 2015, whichapplications are hereby incorporated herein by reference in theirentirety and for all purposes.

GOVERNMENT RIGHTS

This invention was made with government support underSOCOM-H9222-15-C-0017 awarded by the United States Special OperationsCommand, and NASA-NNX14CA56P awarded by National Aeronautics and SpaceAdministration. The government has certain rights in the invention.

BACKGROUND

Exoskeletons can be beneficial in assisting disabled users with mobilityand can also be beneficial in providing users with strength assistanceor providing extra-human abilities. For example, where disabled userslack control over certain parts of their body or have reduced strengthin certain body parts, an exoskeleton can be used to regain mobility orincrease strength in such body parts. In another example, an exoskeletoncan be used to assist users in tasks such as lifting or carrying heavyobjects, which can increase the stamina of the user or provide the userwith additional strength.

Exoskeletons can be coupled with various portions of the body includingthe arms, legs, torso, head, hands and feet. However, conventional legexoskeletons often use an interface between the exoskeleton appendageand the user's foot that is sloppy. Furthermore, force transmission isgenerally effected via a contact point at the heel, which can lead to anonstandard gait, and limit actions such as squatting.

In view of the foregoing, a need exists for an improved lower-legexoskeleton system and method in an effort to overcome theaforementioned obstacles and deficiencies of conventional exoskeletonsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary perspective illustration of a lower-legexoskeleton being worn by a user in accordance with an embodiment.

FIG. 2 is an exemplary close-up illustration of an inflatable actuatorof the example embodiment of FIG. 1.

FIG. 3 illustrates an exoskeleton system that comprises a first andsecond lower-leg exoskeleton that are operably connected to an actuationsystem that includes a pneumatic system and a control system.

It should be noted that the figures are not drawn to scale and thatelements of similar structures or functions are generally represented bylike reference numerals for illustrative purposes throughout thefigures. It also should be noted that the figures are only intended tofacilitate the description of the preferred embodiments. The figures donot illustrate every aspect of the described embodiments and do notlimit the scope of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following disclosure illustrates example embodiments pertaining tothe design of novel exoskeleton orthotics for the ankle, foot, andankle-foot interface, as well as methods for attaching to andtransmitting power through users' feet and/or footwear. Connection tothe feet has remained an unsolved problem in exoskeleton development andvarious systems methods described herein are designed to minimize userdiscomfort through the use of semi-compliant and/or dynamicallyadjustable structures, while maintaining a sufficiently rigid forcetransmission path to allow for efficient power output and control.

The present disclosure teaches the design and implementation of variousexample embodiments of a shoe/orthosis that can work as a standaloneunit, or can be integrated into a robotic exoskeleton in order toprovide control of the ankle. Various preferred embodiments include astructure that allows force to be transmitted directly through the soleof a piece of footwear, without using the user's foot as part of theload path. To accomplish this, in some embodiments, footwear associatedwith an ankle actuator can be modified or specially designed. It can bebeneficial for components within the sole of the shoe to be configuredto receive and transmit actuator load without interfering with theuser's movements or causing damage to the shoe. For example, someembodiments can include a load contact point forward of the heel of auser, such as at or forward of the tarsals or metatarsals.

One embodiment can comprise a specially designed substructure built intothe sole, with exposed external attachment points to create an interfacewith an exoskeleton. These connection points can have quick-connectattachments to make it easier for the user to put on the device. Theseattachment points can be retractable to further improve ease of use whenputting on or taking off the device. The shoe sole substructure can berigid, and/or have a dynamically adjustable stiffness by way ofinflatable structures and/or smart materials. In some embodiments,additional structures in the sole can be used to transmit theexoskeleton's load evenly across the ground, and can be dynamicallyadjustable to compensate for changes in gait due to different operatingconditions (movement speed, terrain, etc.). Accordingly, various exampleembodiments described herein are configured for more comfortable powertransmission through the ankle and provided better range of motioncompared to conventional exoskeletons.

Turning to FIG. 1, an example lower-leg exoskeleton 100 is shown coupledto a user 101 about the leg 102, including the foot 103 and ankle 104.In this example, the lower-leg exoskeleton 100 is shown coupled aboutthe tarsals 105, metatarsals 106, heel 107 and shin 108.

The lower-leg exoskeleton 100 is shown comprising a foot structure 110that is coupled to an actuator 140 at a first actuator end 141, andfurther comprising a shin structure 150 coupled at a second actuator end142. The foot structure 110 is shown including sidewalls 112 and a base114, which define a slot 116 in which the foot 103 of the user 101 canbe disposed. A base strap 120 is illustrated being coupled to the footstructure 110 and encircling a portion of the foot 103. A heel strap 130is illustrated being coupled to the foot structure 110 and encircling aportion of the heel 107.

In this example, the sidewalls 112 define a generally C-shaped portionof the foot structure 110 with the base 114 being substantially planarand engaging a bottom portion of the foot 103. The foot structure 110can be rigid and comprise materials such as plastic, metal or the like.In various embodiments, the base 114 can provide a load-path contactpoint forward of the heel 107 of a user, such as at or forward of thetarsals 105 or metatarsals 106.

In further embodiments, the foot structure 110 can comprise and/or bedefined by inflatable structures that surround portions of the foot 103,including the tarsals 105 and/or metatarsals 106. In other words,structures such as the sidewalls 112, base 114, base strap 120, heelstrap 130, or the like, can comprise an inflatable structure. In oneexample, inflatable structures can be positioned on the sole of the foot103, which can be configured to spread a load generated while walkingevenly across the ground or other surface being walked on.

Although the foot structure 110 is shown in one example configuration inFIG. 1, it should be clear that various other suitable configuration ofa foot structure 110 are within the scope and spirit of the presentdisclosure. For example, a rigid superstructure can attach beneath thesole of the foot 103 and can skirt around the foot 103 to provide aforce transmission platform above the foot 103.

In further embodiments, the lower-leg exoskeleton 100 can be configuredto be worn over clothing and/or footwear such as a conventional boot,shoe, or the like. However, in some embodiments, a portion of thelower-leg exoskeleton 100 can be disposed in, comprise, or be integrallycoupled with a boot, shoe, or the like. In other words, some examplesprovide specialized footwear for use with the lower-leg exoskeleton 100,which can incorporate portions of the lower-leg exoskeleton 100 orotherwise be specifically configured to be used with or coupled with thelower-leg exoskeleton 100. For example, structures such as the sidewalls112, base 114, base strap 120, heel strap 130, or the like, can bedisposed in or be defined by a portion of a shoe or boot.

In another embodiment, a boot or shoe can comprise a segmented structurethat comprises a system of rigid panels connected by a flexible joint(e.g., an elastomer) that allows for in-plane rotation, (e.g., in theplane described as where the ankle rotates towards and away from theshin), and/or lateral motion. In a further embodiment, a structure inthe heel of a shoe or boot can be configured to provide a load path fora reaction force that acts to lift the heel 107 of the user 101.

FIG. 1 illustrates an example composite structure that can act as anankle actuation and passive support structure for a single sided, singledegree-of-freedom (DOF) ankle actuator. The example configuration shownin FIG. 1 comprises an inflatable actuator 140 coupled with rigidpassive components (e.g., the foot structure 110 and the shin structure150) to transfer torque generated by the actuator 140 to the user 101.Accordingly, in various embodiments, one or more rigid componentsassociated with the sole of the foot 103 can be of sufficient instrength to take the load of the actuator 140. In various embodiments asdescribed in further detail herein, the inflatable actuator 140 canprovide a moment about the ankle 104 of the user 101. For example, thefoot structure 110 can be connected via a feature in the sole of a shoethat allows the user 101 to dorsiflex and/or plantar flex his or herfoot 103.

Plantarflexion torque can be provided by inflating the actuator 140. Inthis example configuration, the actuator 140 may only connect to thefootwear at a load transmission point, but this should not be construedto limit the many alternative embodiments of the design. Other versionsof this system can be integrated in various suitable ways. For example,in some cases, the actuator 140 and footwear can encompass a singlepiece of hardware that is designed for a specific user (or for aspecific size leg and foot), and thus can be smaller in someembodiments.

In some embodiments the rigid foot structure 110 comprises: a pair ofsidewalls 112 configured to extend around the foot 103 of a user 101 andincluding first and second sidewall attachment points 115 respectivelyon the sidewalls 112 for attachment with a removable base portion 117,and a removable flat base portion 117 configured to reside at the baseof the foot of the user that includes first and second base attachmentpoints 119 configured for removably coupling with the first and secondsidewall attachment points, the removable flat base portion 117integrally disposed within and extending through the sole of a footweararticle 109 with the first and second base attachment points 119disposed on respective external sides of the footwear article 109.

In some embodiments, the rigid foot structure 110 further comprises aninflatable structure 121. In some embodiments, an inflatable structure121 is positioned at the sole of a foot of a user and configured toevenly spread a load on a surface generated while the user is walking onthe surface. In some embodiments, the rigid shin structure furthercomprises an inflatable structure 151.

FIG. 2 depicts a close-up view of the inflatable actuator 140 of FIG. 1,which illustrates that the example actuator 140 can comprise a pluralityof stacked inflatable bladder segments 210, which are separated by aplurality of collars 220 that are stacked between respective bladdersegments 210. In some embodiments, the bladder segments 210 can compriseinternally separate cavities or can comprise an internallyinterconnected cavity. For example, in some embodiments, the collars 220can physically separate respective internal cavities of respectivebladder segments 210. In some embodiments, the collars 220 can bedefined by a seam, pucker, or the like. In further embodiments, thecollars 220 can be absent.

As illustrated in FIGS. 1 and 2, the bladder segments 210 and collars220 can extend around and surround a front portion of the foot 103 of auser 101. More specifically, the bladder segments 210 and collars 220can extend from a front portion 230 to rear portions 240 at the side orrear of the foot 103. Inflation of the bladder segments 210 can resultin expansion of the bladder segments 210, and in this example, theactuator 140 can be configured for larger expansion at the front portion230 relative to the rear portions 240.

Accordingly, the inflatable actuator 140 can provide a moment about theankle 104 of the user 101 due to the difference in expansion of thebladder segments 210 between the front and rear portions 230, 240. Forexample, inflation of the actuator 140 can generate a moment that forcesthe shin structure 150 toward the shin 108 of the user, and a momentthat generates plantar flexion of the foot 103. In other words, the shinstructure 150 engaging the shin 108 opposes the actuator 140 such that arotation generated by the actuator 140 during inflation results inrotation of the foot 103. Additionally, the collars 220 can provide forstabilization of the bladder segments 210, which can generate uniformexpansion of the actuator 140 while being inflated.

Although a generally C-shaped inflatable actuator 140 is illustrated inthe example embodiment of FIGS. 1 and 2, in further embodiments, othersuitable actuators and actuator configurations can be used. For example,in one embodiment, an actuator 140 can be powered in other suitable waysincluding via a motor, or the like. Additionally, in another example, anactuator can include elongated segments positioned along the length ofthe shin 108 at the front of the foot 103, which can be configured toexpand and curl lengthwise to generate a moment that causes plantarflexion of the foot 103. In a further example, an actuator 140 cancompletely surround the foot 103. Accordingly, it should be clear thatthe example actuator 140 illustrated in this disclosure should not beconstrued to be limiting on the many alternative actuators that arewithin the scope and spirit of the present invention.

FIG. 3 illustrates an exoskeleton system 300 that comprises a first andsecond lower-leg exoskeleton 100 that are operably connected to anactuation system 310 that includes a pneumatic system 320 and a controlsystem 330. The pneumatic system 320 is shown being operably connectedto the actuators 140 and to the control system 330. The control system330 is illustrated being operably connected to one or more portions ofthe lower-leg exoskeletons 100 and to the pneumatic system 320.

In various embodiments, the pneumatic system 320 can be configured toinflate and/or deflate the actuators 140 with a fluid. For example, inone embodiment, the pneumatic system 320 can only be configured toactively inflate the actuators 140 to cause expansion of the actuators140 and plantar flexion, where deflation can be generated during contactwith the ground during walking and where natural dorsiflexion occurs. Inanother embodiment, the pneumatic system 320 can be configured toactively inflate the actuators 140 to cause expansion of the actuators140 and plantar flexion, and can actively generate dorsiflexion byactively evacuating fluid from the actuators 140 and/or by generatingrelease of fluid from the actuators 140.

Alternatively, in some embodiments, the actuators can be configuredoppositely. For example, inflation of the actuator 140 can causedorsiflexion of the foot 103 and deflation can cause or be caused byplantar flexion of the foot 103. Additionally, although the example of apneumatic system 320 is provided, which actuates the actuators 140 via agas fluid (e.g., air), in further embodiments, the actuators 140 canoperate via any suitable fluid, including water, oil, or the like.

In some embodiments, inflatable actuators can be positioned in otherlocations in addition to or alternatively to the inflatable actuator 140illustrated in FIGS. 1-3. For example, one or more actuator can bepositioned about the sole of the foot 103, at the heel 107, or the like.Such additional or alternative actuators can be configured to generatevarious types of movement of the foot 103, including inversion,eversion, plantar flexion, dorsiflexion, flexion of a toe, extension ofa toe, and the like. Additionally, various suitable portions of alower-leg exoskeleton 100 can comprise inflatable support structures asdiscussed herein.

The control system 330 can be associated with various suitable portionsof the lower-leg exoskeleton 100 and can be associated with one or moresuitable sensors. For example, sensors can determine a position,movement, rotation or orientation of the foot 103 and/or portion of thelower-leg exoskeleton 100. Additionally, and alternatively, such sensorscan determine an inflation state of an actuator 140, a pressureassociated with an actuator 140, or the like. Additionally, andalternatively, such sensors can measure body and/or environmentalconditions such as temperature, moisture, salinity, blood pressure,oxygen saturation, muscle tension, and the like.

In various embodiments, the control system 330 can sense conditionsassociated with the lower-leg exoskeletons 100 and inflate and/ordeflate the actuators 140 in response. In some embodiments, the controlsystem 330 can generate a walking gait for a user 101 of the lower-legexoskeletons 100 by selective inflation and/or deflation of theactuators 140. In other embodiments, the control system 330 can identifyand support movements of a user 101 associated with the lower-legexoskeletons 100. For example, the control system 330 can determine thata user 101 is lifting a heavy object and provide enhancing support tothe user 101 in lifting the object by selective inflation and/ordeflation of the actuators 140.

Accordingly, the present example embodiment shown in FIGS. 1-3 shouldnot be construed to be limiting on the wide variety of alternativeembodiments that are within the scope and spirit of the presentinvention. For example, in some embodiments, the control system 330 cancomprise sensors such as ground reaction force sensors embedded in thesole of the shoe along with pressure and angle sensors to measure theeffort of the actuation. Muscle activation sensors can also beintegrated into footwear to allow for feedback control by the controlsystem 330.

A further embodiment of the sole design can incorporate an actuatordirectly into the sole of an article worn by a user. Such an actuatorcan work as a standalone device or in concert with other portions of alower-leg exoskeleton 100 to provide motive force by direct manipulationof the sole.

To anchor the forefoot in place and transmit load to the sole,structures can be built around the tarsal 105 and metatarsal 106 areasof the foot 103 in accordance with various embodiments. For example, inone embodiment, these structures can be simple rigid structures (whichcan be solid structures, and/or passive inflatable structures) thatprovide a repeatable load path. In other iterations, such structures canbe dynamically adjustable via the use of smart materials; by adjustingthe pressure of inflatable chambers; and the like.

As loading in some embodiments occurs at or near the ball of the foot103, additional structure(s) can be added in some embodiments to theheel area 107, to help ensure that ankle 104 pivoting occurs in thedesired location, to provide stability, and the like. In someembodiments, an ankle actuator 140 can comprise a two part, antagonisticdesign. For example, a pair of actuators 140 can provide a load path forforce creating dorsiflexion and/or plantar flexion via inflation and/ordeflation of the actuators 140.

In further embodiments, especially those designed for high performance(high speed, high force output), the shin structure 150 can bebeneficial to distribute the force created by the ankle actuator 140 asdiscussed herein. This shin structure 150 can be built into the actuator140, and connect to set attachment points on an article worn by a user,or the article can have an integrated shin support or shin structure150. The shin structure can include rigid and/or inflated passivestructures positioned over the shin 108 to distribute load to the shin108 during actuation of the lower-leg exoskeletons 100.

To connect rigid structures above and below the ankle, flexiblematerials can be used to create a pivot that allows for both lateralmovement and rotation of the shin relative to the ankle. In someembodiments, some or all force transmission structures can be createdthrough the use of passively inflated structures, which can be deflatedto allow for a comfortable and un-intrusive resting state when thesystem is not in active use. Additionally, by integrating attachmentpoints, sensing, and load transfer structures directly into footwear,and transmitting force through the ball of the foot in accordance withsome embodiments, it is possible to create a more efficient system thatis less intrusive and more comfortable for the user.

One embodiment can comprise a specially designed substructure built intothe sole, with exposed external attachment points to create an interfacewith an exoskeleton. These connection points can have quick-connectattachments to make it easier for the user to put on the device. Theseattachment points can be retractable to further improve ease of use whenputting on or taking off the device. The shoe sole substructure can berigid.

For example, referring to FIG. 1, in one embodiment, the base portion114 of the foot structure 110 can be removable from the sidewalls 112via first and second attachments, which can any suitable attachmentmechanism including a hook, slot, bolt, clip, knob, or the like. In someembodiments, the base portion 114 can be integrally disposed within oraffixed within footwear such as a shoe or boot.

In other words, the removable base portion 114, having attachment pointon a first and second end, can extend through the sole of a boot or shoewith the attachment points exposed on respective external sides of theshoe for attachment with a lower-leg exoskeleton 100. The attachmentpoints can correspond to and be configured for coupling with attachmentstructures of the sidewalls 112 or the like. Such embodiments can bedesirable and provide for quick attachment and detachment of thelower-leg exoskeleton 100 to and from conventional footwear.

In alternative embodiments, attachment points of the base portion 114can be configured for attachment at various suitable positions in, on orabout a shoe, boot, or the like. For example, in one embodimentattachment points of the base portion 114 can be positioned within ashoe or boot cavity. Such embodiments can be desirable for providing aconnection with the lower-leg exoskeleton 100 which is less obtrusiveand observable to others. In a further embodiment, the base portion 114can comprise a rigid insert configured to be disposed over or within theinsole of a shoe or boot and such an insert can comprise attachmentpoints as discussed above or can be integrally attached to the sidewalls112 or other suitable portion of a lower-leg exoskeleton 100.

The described embodiments are susceptible to various modifications andalternative forms, and specific examples thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the described embodiments are not to belimited to the particular forms or methods disclosed, but to thecontrary, the present disclosure is to cover all modifications,equivalents, and alternatives.

What is claimed is:
 1. A lower-leg exoskeleton comprising: a singledegree-of-freedom (DOF) ankle actuator that is configured to be wornover a portion of a foot of a user and configured to be worn disposedadjacent to an ankle of the foot of the user at least on the lateralside of the lower leg of the user; a rigid foot structure coupled to afirst actuator end of the actuator, the rigid foot structure configuredto surround a portion of the foot of the user, wherein the rigid footstructure comprises: one or more sidewalls configured to extend aroundthe foot of the user and including first and second sidewall attachmentpoints for connecting to a base portion, and the base portion integrallybuilt into a rigid sole of a boot or shoe, the base portion configuredto reside at a base of the foot of the user and including exposedexternal first and second base attachment points coupling with the firstand second sidewall attachment points; and a rigid shin structurecoupled at a second actuator end of the actuator, the rigid shinstructure configured to couple and engage with a shin of the userwherein, the actuator and rigid foot structure are configured to, whenworn by the user, receive and transmit an actuator load generated by theactuator around the foot of the user to a load contact point of thelower-leg exoskeleton configured to be disposed at a bottom of the footof the user defined by the rigid foot structure and generate a momentthat forces the rigid shin structure toward the shin of the user suchthat the rigid shin structure engaging the shin of the user opposes theactuator such that the moment generated by the actuator results inflexion of the foot of the user.
 2. The lower-leg exoskeleton of claim1, wherein the base portion is integrally built into the rigid sole ofthe boot or shoe and allows force to be transmitted directly through therigid sole of the boot or shoe without using the foot of the user aspart of a load path for the moment generated by the actuator thatresults in flexion of the foot of the user.
 3. The lower-leg exoskeletonof claim 1, wherein the rigid foot structure is coupled to a firstactuator end of the actuator and comprises a heel structure in a heel ofthe shoe or boot configured to provide a load path for force generatedby the actuator that results in the flexion of the foot of the user. 4.A robotic exoskeleton system comprising: a first lower-leg exoskeletonof claim 1 coupled to a left leg of the user; a second lower-legexoskeleton of claim 1 coupled to a right leg of the user; and a controlsystem configured to sense conditions associated with the first andsecond lower-leg exoskeletons via one or more sensors and providefeedback control for the robotic exoskeleton system by selectivelyactuating the respective actuators of the first and second lower-legexoskeletons in response to the sensed conditions, the feedback controlgenerating a walking gait for the user wearing the first and secondlower-leg exoskeletons by the selective actuation of the respectiveactuators, wherein sensing conditions associated with the first andsecond lower-leg exoskeletons includes determining a position, movement,rotation and orientation of the left and right legs of the user and/or aposition, movement, rotation and orientation of the first and secondlower-leg exoskeletons.
 5. A lower-leg exoskeleton comprising: an ankleactuator that is configured to be worn above a foot of a user andconfigured to be worn disposed below the knee of the user; a rigid footstructure coupled to a first actuator end of the actuator, the rigidfoot structure configured to surround a portion of the foot of the user,wherein the rigid foot structure comprises: one or more sidewallsconfigured to extend around the foot of the user and including first andsecond sidewall attachment points for connecting to a base portion, anda base portion configured to reside at a base of the foot of the userand including exposed external first and second base attachment pointscoupling with the first and second sidewall attachment points; and arigid shin structure coupled at a second actuator end of the actuator,the rigid shin structure configured to engage with a shin of the user.6. The lower-leg exoskeleton of claim 5, wherein the actuator is asingle degree-of-freedom (DOF) actuator that provides no more than oneDOF.
 7. The lower-leg exoskeleton of claim 5, wherein the base portionis integrally built into a rigid sole of a boot or shoe.
 8. Thelower-leg exoskeleton of claim 5, wherein, the actuator and rigid footstructure are configured to, when worn by the user, receive and transmitan actuator load generated by the actuator around the foot of the userto a load contact point of the lower-leg exoskeleton configured to bedisposed at a bottom of the foot of the user defined by the rigid footstructure.
 9. The lower-leg exoskeleton of claim 5, wherein, theactuator is configured to generate a moment that forces the rigid shinstructure toward the shin of the user such that the rigid shin structureengaging the shin of the user opposes the actuator such that the momentgenerated by the actuator results in flexion of the foot of the user.10. The lower-leg exoskeleton of claim 5, wherein the base portion isintegrally built into a rigid sole of a boot or shoe and allows force tobe transmitted directly through a heel structure in a heel of the rigidsole of the boot or shoe without using the foot of the user as part of aload path for a moment generated by the actuator that results in flexionof the foot of the user.
 11. A lower-leg exoskeleton comprising: anactuator configured to be worn about a portion a leg of a user that isbelow the knee of the user; and a foot structure coupled to a firstactuator end of the actuator, the foot structure configured to surrounda portion of the foot of the user, wherein the foot structure comprises:one or more sidewalls configured to extend around the foot of the userand including one or more sidewall attachment points for connecting to abase portion, and a base portion configured to reside at a base of thefoot of the user and including one or more base attachment pointscoupling with the one or more sidewall attachment points.
 12. Thelower-leg exoskeleton of claim 11, wherein the actuator is configured tobe worn disposed adjacent to an ankle of the foot of the user.
 13. Thelower-leg exoskeleton of claim 11, further comprising a shin structurecoupled at a second actuator end of the actuator, the shin structureconfigured to engage with a shin of the user.
 14. The lower-legexoskeleton of claim 11, wherein the actuator is a singledegree-of-freedom (DOF) actuator that provides no more than one DOF. 15.The lower-leg exoskeleton of claim 11, wherein the base portion isintegrally built into a sole of a boot or shoe.
 16. The lower-legexoskeleton of claim 11, wherein, the actuator and foot structure areconfigured to, when worn by the user, receive and transmit an actuatorload generated by the actuator around the foot of the user to a loadcontact point of the lower-leg exoskeleton configured to be disposed ata bottom of the foot of the user defined by the foot structure.
 17. Thelower-leg exoskeleton of claim 11, wherein, the actuator is configuredto generate a moment that forces the shin structure toward the shin ofthe user such that the shin structure engaging the shin of the useropposes the actuator such that the moment generated by the actuatorresults in movement of the foot of the user.
 18. The lower-legexoskeleton of claim 11, wherein the base portion is integrally builtinto a sole of a boot or shoe and allows force to be transmitteddirectly through a heel structure in a heel of the sole of the boot orshoe without using the foot of the user as part of a load path for amoment generated by the actuator that results in movement of the foot ofthe user.
 19. A robotic exoskeleton system comprising: a first lower-legexoskeleton of claim 11 coupled to a left leg of the user; a secondlower-leg exoskeleton of claim 11 coupled to a right leg of the user;one or more sensors; and a control system configured to provide feedbackcontrol for the first and second lower-leg exoskeleton based on datafrom the one or more sensors.
 20. The robotic exoskeleton system ofclaim 19, wherein the control system is configured to sense conditionsassociated with the first and second lower-leg exoskeletons via the oneor more sensors and provide feedback control for the robotic exoskeletonsystem by selectively actuating the respective actuators of the firstand second lower-leg exoskeletons in response to the sensed conditions,the feedback control generating a walking gait for the user wearing thefirst and second lower-leg exoskeletons by the selective actuation ofthe respective actuators, wherein sensing conditions associated with thefirst and second lower-leg exoskeletons includes determining at leastone of a position, movement, rotation and orientation of the left andright legs of the user and/or at least one of a position, movement,rotation and orientation of the first and second lower-leg exoskeletons.